Since glutamine, alanine and other non-essential amino acids are the major carriers for the transport of nitrogen in various body compartments, we would like to examine the nitrogen and carbon kinetics of a number of key non-esssential amino acids such as alanine, glycine, and serine. These studies will examine the hypotheses that with advancing gestation, as protein oxidation decreases, there is increased sythesis of non-essential amino acids. We will quantify,using isotopic tracer dilution methods, the rate in production and utilization of serine, its contribution to glucose, the impact of glucose infusion on serine turnover, and the relation between serine and glycine nitrogen. In a parallel series of experiments, we will quantify the release of alanine nitrogen from the forearm muscle and its incorporation in urea. Subjects to be studied include normal subjects, women with gestational diabetes and insulin-dependent diabetes and mothers with intrauterine growth restricted fetuses. Normal subjects will be studied longitudinally during the first and third trimester of pregnancy. The abnormal groups will be studied only in the third trimester. These studies are important because they further add to our understanding of nitrogen conservation and nitrogen accretion by the mother, and in the long run we anticipate that they will give us an insight into the mechanism of nitrogen conervation by the mother, and potentially in other situation of nitrogen accretion, such as puberty, in newborn babies, and following growth hormone therapy.